The present invention relates to a method of repairing an existing pipeline, particularly to a method of repairing an existing underground pipeline including a main pipe and a branch pipe.
There have been known various sorts of methods for repairing an existing underground pipeline not involving excavation. One of them is to repair an existing pipe by coating the internal surface thereof with a resin, as disclosed by the applicant in Japanese Patent Application Laid No. 4-114773.
In the method according to Japanese Patent Application Laid-open No. 4-114773, an existing old pipe to be repaired is a gas service pipe buried underground, which is extending from a gas main on road side to a user's house. At first, a gas meter attached at an outer end of a gas service pipe is removed therefrom so that said outer end is exposed to become an open end. Then, a predetermined amount of liquid resin is introduced into the service pipe. Subsequently, a predetermined amount of a pressurized liquid is introduced into the service pipe, so that the liquid resin is forced to flow forward along the pipe in a plug-flow until it arrives at an inner end of the pipe. Afterwards, a suction equipment such as a suction pump is connected to the open end of the service pipe, said suction pump is then driven to produce a suction force to draw the liquid back out of the service pipe. In this way, the liquid resin is caused to flow back from the inner end of the pipe and moves through the entire length thereof, thereby coating the pipe internal surface with the liquid resin and forming a desired resin lining layer thereon.
However, the above-discussed method has been proved to have at least the following problems.
Namely, an amount of a pressurized liquid necessary to force the liquid resin to move forward in the service pipe is usually calculated by taking into account a pipe length, a pipe diameter and a volume of the liquid resin. In practice, the pipe length is defined to be a distance extending from the above open end to the above inner end (a position involving a service tee adjacent to a gas main), and such distance is measured in advance with the use of an acoustic wave pipe length measuring device.
However, the above-discussed method is found to be difficult for treating a gas service pipe involving a branch pipe (which is a further pipe branching from the service pipe). Namely, when the above method is used to repair an existing service pipe involving a branch pipe, an acoustic wave emitted into the service pipe for measuring its length (extending from the above open end to the above inner end) will be undesirably dispersed into the branch pipe. As a result, some undesired reflected waves will also be picked up, making it difficult to perform a correct measurement of the length of the service pipe which is to be repaired in a resin lining treatment. Moreover, when a liquid resin and a pressurized liquid are moving in the service pipe, they will undesirably flow into the branch pipe. Thus, it is in fact impossible to perform a desired resin lining treatment on an existing gas service pipe if it includes a branch pipe.